An integrated circuit comprises metal pads intended to provide connections to the outside. Some of the pads are capable of receiving power supply voltages. The other pads are capable of receiving and/or of supplying input-output signals. Power supply rails, coupled to the power supply pads, are generally provided at the periphery of the circuit to power its different components. Generally, an insulating layer covers the circuit, only leaving access to the metal pads.
Such a circuit generally receives and/or supplies signals at a low voltage level (for example, from 1 to 5 V) and at a low current intensity (for example, from 1 μA to 10 mA), and is likely to be damaged when overvoltages or overintensities occur between pads of the circuit.
It is thus provided to associate a protection structure with each pad. The protection structure should be able to rapidly drain off significant currents, capable of occurring when an electrostatic discharge occurs between two pads of the circuit.
U.S. Pat. No. 6,765,771 describes an example of a protection structure comprising a thyristor.